Device for use in a method for the production of a protective layer and method for the production of a protective layer

ABSTRACT

A device for use in a method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade, is disclosed. The device includes a pouch-, bag- or sack-like receiving device for receiving the hard material particles and is made of a net-, screen- or non-woven-like material that is pervious to an electrochemical coating solution and has a mesh size smaller than the diameter of the hard material particles. The receiving device is designed such that it can be removably attached with an opening over and around a region of the component to be coated. A method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine using a pouch-, bag- or sack-like receiving device filled with hard material particles, is also disclosed.

This application claims the priority of International Application No. PCT/DE2009/000771, filed Jun. 3, 2009, and German Patent Document No. 10 2008 026 936.0, filed Jun. 5, 2008, the disclosures of which are expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a device for use in a method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade. The invention also relates to a method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade.

To increase the efficiency, performance and service life of turbomachines, particularly of gas turbines in engine building, the component surfaces are increasingly being provided with various coatings. In engine building, this results in respectively improved aerodynamics, higher possible combustion temperatures and higher possible mechanical stress of the individual components. Thus, for example the efficiency of the turbomachine is codetermined in particular by the rotor gap between the tips of the rotor blades and the wall of the rotor housing facing the rotor or the rotor blades. In order to keep this gap as small as possible, a so-called air seal is used, wherein the air seal is defined by so-called running-in coatings on the inner side of the housing and correspondingly hard coatings on the blade tips. Applying a so-called blade tip armoring significantly reduces the wear on the blade tip during the so-called running-in in the running-in coating. The galvanic application of abrasive particles is known in the case of turbine blades. Corresponding methods are described in U.S. Pat. Nos. 5,665,217, 5,437,724, and 5,074,970. In this case, to coat the blade tips, hard material particles are made available in an immersion bath featuring an electrolyte, which are applied to the corresponding blade tip during galvanizing with the metallic matrix layer, particularly with a nickel layer. In the process, the hard material particles are embedded in the galvanically applied metallic matrix layer. However, the disadvantage of the known method and devices is that they are relatively involved, because, among other things, structurally complicated devices are used for the galvanizing process. In addition, very high quantities of hard material particles are used to achieve the desired concentrations on the blade tips. Hard material particles, such as, for example, hard material particles made of (cubic) boron nitride, are very expensive, however, so that the use of the known method is very expensive as a whole. In order to reduce these costs, an attempt was made in accordance with German Patent Document No. DE 3525079 A1 to arrange the hard material particles or abrasive particles on an electrically non-conductive porous band. The disadvantage, however, is that the abrasive particles are fastened to the band by means of an adhesive layer and after galvanizing and applying the abrasive particles to the corresponding component surface, this adhesive connection must be separated again. This results in a relatively complicated process flow.

As a result, the object of the present invention is providing a generic device for use in a method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade, which guarantees a simplified and more cost-effective process flow.

The object of the present invention is also to make available a generic method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade, which guarantees a simplified and more cost-effective process flow.

A device according to the invention for use in a method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade includes a pouch-, bag- or sack-like receiving device for receiving the hard material particles, wherein the receiving device is made of a net-, screen- or non-woven-like material that is pervious to an electrochemical coating solution and has a mesh size smaller than the diameter of the hard material particles. In addition, the receiving device is designed such that it can be removably attached with an opening over and around a region of the component to be coated. Attaching the receiving device over or around the region of the component to be coated makes it possible to make a defined quantity of hard material particles available for the coating. An unnecessary use of hard material particles cannot take place because the receiving device collects the hard material particles possibly not used for the coating so that they may be used again for a subsequent coating process. In addition, attaching the receiving device over and around the region of the component to be coated can be accomplished simply and quickly so that the process flow as a whole is greatly simplified.

In advantageous embodiments of the device according to the invention, the opening of the receiving device is surrounded by a flexible seal. In particular, the seal is laminated into the edge of the opening. Due to the embodiment of a flexible seal on the edge of the opening of the receiving device, it is possible for it to be readily fastened securely to the component to be coated, for example, a blade tip of a rotor. The formation of a seal also guarantees that the hard material particles are only applied in the regions of the component that are actually to be coated.

In other advantageous embodiments of the device according to the invention, the receiving device is connected in the region of its opening to an attachment base plate in such a way that the opening corresponds with an opening in the attachment base plate and the attachment base plate can be removably fastened to a cover. In this case, the cover has at least one orifice for receiving the regions of the component to be coated, wherein the opening of the attachment base plate is positioned over these regions with the opening of the receiving device. Such an embodiment of the device guarantees a secure and defined receiving of the regions of the component to be coated in the cover and a corresponding positioning of the receiving device containing the hard material particles over and around the regions of the component to be coated. The use of this type of receiving device simplifies the process flow, because the receiving device containing the hard material particles may be positioned readily and securely. In addition, the opening of the attachment base plate may be surrounded by at least one seal. This also guarantees that the hard material particles are made available actually only in the regions of the component that are to be coated. In addition, at least one fixation pin for insertion into a corresponding fixation opening of the cover may be configured on the side of the attachment base plate opposite from the receiving device. This guarantees an exact, simple and secure positioning of the receiving device on the cover. In another embodiment of the device according to the invention, the cover has at least one fixation device for removably fastening the cover to the component. This also makes a secure positioning of the cover on the desired component surfaces possible. In addition, it is possible for a seal surrounding the opening with a positive fit to be configured between the attachment base plate and the orifice. This guarantees that the hard material particles are embedded with the aid of the galvanically applied metallic matrix layer only in the regions of the component actually to be coated. The hard material particles in this case may be made of (cubic) boron nitride, ceramic, titanium carbide, tungsten carbide, chromium carbide, aluminum oxide or zirconium oxide or a mixture thereof. The particle size is normally between 30 to 200 μm, however, other particles sizes may also be used. The cover may be configured to be rigid or flexible.

An inventive method for the galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, particularly a blade tip armoring of a blade tip of a rotor blade includes the following steps:

a) Attachment of an opening of a pouch-, bag- or sack-like receiving device of a device filled with hard material particles over and around a region of the component to be coated, wherein the receiving device is made of a net-, screen- or non-woven-like material that is pervious to an electrochemical coating solution and has a mesh size smaller than the diameter of the hard material particles;

b) Placement of at least the regions of the component to be coated into an immersion bath with the electrochemical coating solution and application of a voltage for forming a metallic matrix layer at least on the region of the component to be coated with the embedding of the hard material particles; and

c) Galvanic formation of a filler layer between the embedded hard material particles.

The method according to the invention guarantees a simplified and cost-effective process flow. In particular, a sufficiently high concentration of hard material particles is made available for the coating without the particles being distributed freely and in an uncontrolled manner in the electrochemical coating solution. In addition, the attachment of the receiving device over and around the region of the component to be coated is simple to carry out in terms of the process. In the case of the method according to the invention, unneeded hard material particles remain in the receiving device. They may then be used readily for a subsequent coating step provided that the concentration of hard material particles is still sufficient. Because the receiving device is made of a material that is pervious to the electrochemical coating solution, the galvanic process, i.e., the formation of a metallic matrix layer, especially a layer containing nickel, on the region of the component to be coated with the embedding of hard material particles is not hindered. The galvanic formation of the filler layer between the embedded hard material particles in accordance with the process step c) may be carried out for example after a removal of the receiving device.

In a further advantageous embodiment of the method according to the invention, in process step c), a rotation of the component is carried out, wherein the axis of rotation of the component runs horizontally. The rotational movement of the component guarantees a uniform distribution of the hard material particles on the component surface to be coated. Because of gravity, the hard material particles in an upper position of the rotating component are pressed against the component surface to be coated. In this case, the component is placed completely into the immersion bath with the electrochemical coating solution. However, it is also possible for the component to be immersed only partially or in sections into the galvanic immersion bath. Especially in the case of integrally bladed rotor disks or rotor rings (BLISK or BLING), the desired uniform distribution of the hard material particles on the blade tips is produced because of the rotation of the BLISK or BLING with a horizontally aligned axis of rotation.

In another advantageous embodiment of the method according to the invention, in process step a), the receiving device with the opening is put over the region of the component to be coated with a positive fit, wherein the opening is surrounded by a flexible seal. The flexible seal in this case may be laminated into the edge of the opening. Putting the receiving device over the component region to be coated with a positive fit guarantees that only these regions, i.e., the desired component regions, are coated. In addition, the cited placement process may be carried out simply and quickly.

In a further advantageous embodiment of the method according to the invention, the receiving device is connected in the region of its opening to an attachment base plate in such a way that the opening of the receiving device corresponds with an opening in the attachment base plate and the attachment base plate can be removably fastened to a cover. The cover in this case has at least one orifice for receiving the regions of the component to be coated, wherein, in process step a), the opening of the attachment base plate is positioned over these regions with the opening of the receiving device. This process step also guarantees that only predetermined regions of the component are coated with the protective layer featuring the hard material particles. In addition, the to-be-coated components or component regions may be positioned with a positive fit in the cover quickly and simply by means of the cited orifices.

In other advantageous embodiments of the method according to the invention, the cover is removably fastened to the component prior to the process step a). In this case, the cover is designed such that it can accommodate one or more to-be-coated component regions in corresponding orifices. In addition, the cover may be configured to be flexible or rigid.

In another advantageous embodiment of the method according to the invention, the electrochemical coating solution used in process step b) and/or the process step c) contains nickel. This may be a nickel sulfamate solution in particular. However, it is also possible for the anode projecting into the galvanic immersion bath to use a solid nickel anode. Other metallic coating materials are also conceivable and are based in particular on the metallic composition of the component to be coated. The hard material particles used are normally made of (cubic) boron nitride, ceramic, titanium carbide, tungsten carbide, chromium carbide, aluminum oxide or zirconium oxide or a mixture thereof. Typical grain sizes of the hard material particles used are between 30 μm and 200 μm. Other grain sizes may also be used.

In a further advantageous embodiment of the method according to the invention, the filler layer formed in process step c) fills in the space between the hard material particles, wherein the hard material particles are integrated geometrically into the filler layer in a range between 65-90%. This results advantageously in a secure fixation of the hard material particles in the metallic matrix, wherein it is also guaranteed that a sufficiently large region of the hard material particles still projects from the matrix surrounding it.

In other advantageous embodiments of the method according to the invention, prior to the process step a), a cleaning and/or a covering of the components takes place with a subsequent removal of the cover in the regions to be coated and/or chemical pretreatment at least of the regions of the component to be coated. These measures serve to connect the metallic matrix of the applied protective layer readily to the metallic component surface. The type of pretreatment depends upon the composition of the component to be coated. Thus, the pretreatment of titanium components may include the following steps, for example:

1. Etching of the component in an acidic solution containing nitric acid as well as fluoride;

2. Actively pickling the etched component in a solution containing at least sodium nitrate or tetrafluoroboric acid; and

3. Activation of the actively pickled component in an acidic bath or an acid bath containing nickel. After this type of pretreatment, the layer containing the hard material particles may be applied directly.

A component according to the invention is produced according to a method described in the foregoing, wherein the component is particularly a blade tip of a rotor blade of a compressor of an aircraft engine, particularly a BLISK or BLING. These bladed disks or rings are made in particular of titanium alloys or nickel alloys. However, it is also possible for these components to be produced from metal matrix composite materials having a titanium basis. It is also possible for these components to be made of so-called intermetallic materials of the type TiAl or Ti₃Al.

Additional advantages, features and details of the invention are disclosed in the following description of a graphically depicted exemplary embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a device according to the invention; and

FIG. 2 is a schematic representation of a receiving device of the inventive device according to FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a device 10 for use in a method for the galvanic production of a protective layer featuring hard material particles on a component 38 of a turbomachine. The depicted exemplary embodiment shows a blade tip armoring of a blade tip 34 of a rotor blade 42. One can see that the device 10 has a bag-like receiving device 12 for receiving the hard material particles 14 (see FIG. 2), wherein the receiving device 12 is made of a net-, screen- or non-woven-like material that is pervious to an electrochemical coating solution and has a mesh size smaller than the diameter of the hard material particles 14. In addition, the receiving device 10 is designed such that it can be removably attached with an opening 16 (see FIG. 2) over and around the region 40 of the component 38 to be coated. In the depicted exemplary embodiment, the receiving device 12 is connected in the region of its opening 16 to an attachment base plate 18, wherein the opening 16 corresponds with an opening 20 in the attachment base plate 18. The attachment base plate 18 in this case can be removably fastened to a cover 24. The fastening is carried out in the depicted exemplary embodiment through fixation pins 28, which are arranged on the side of the attachment base plate 18 opposite from the receiving device 12 and can be inserted into corresponding fixation openings 30 of the cover 24 (see FIG. 2).

One can also see that the cover 24 has several orifices 26 for receiving the blade tips 34 or the regions 40 of the component 38 to be coated. For the coating process, the opening 20 of the attachment base plate 18 is positioned with the opening 16 of the receiving device 12 over the blade tips 34 or the regions 40 to be coated. One can see that the individual orifices 26 are surrounded respectively by a seal 36 with a positive fit. The seal 36 in this case ends up between the attachment base plate 18 and the cover 24. The seal 36 is normally made of wax or rubber.

In addition, one can see that fixation devices 32 for removably fastening the cover 24 to the component 38 are configured on the cover 24. The to-be-coated blade tip 34 of the rotor blade 42 in the depicted exemplary embodiment is made of a titanium alloy.

FIG. 2 show a schematic representation of the receiving device 12. One can see that the hard material particles 14 are concentrated in the receiving device 12 that is configured in a bag-like and non-woven-like manner. Normally, the hard material particles 14 are made of cubic boron nitride. In addition, one can see that the opening 16 of the receiving device 12 is connected to the attachment base plate 18 in such a way that the opening 16 corresponds with the opening 20 in the attachment base plate 18. In addition, it is clear that the opening 20 in the attachment base plate is surrounded by a seal 22. In addition, the two fixation pins 28 are arranged on the attachment base plate 18. 

1.-19. (canceled)
 20. A device for use in a method for galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, comprising: a pouch-, bag- or sack-like receiving device for receiving hard material particles, wherein the receiving device is made of a net-, screen- or non-woven-like material that is pervious to an electrochemical coating solution and wherein the receiving device includes an opening; an attachment base plate, wherein the receiving device is connected in a region of the opening to the attachment base plate such the opening corresponds with an opening in the attachment base plate; and a cover, wherein the attachment base plate is removably fastenable to the cover, wherein the cover has an orifice for receiving the region of the component, and wherein the opening of the attachment base plate and the opening of the receiving device are positioned over the orifice.
 21. The device according to claim 20, wherein the opening of the receiving device is surrounded by a flexible seal.
 22. The device according to claim 21, wherein the seal is laminated into an edge of the opening.
 23. The device according to claim 20, wherein the opening of the attachment base plate is surrounded by a seal.
 24. The device according to claim 20, further comprising a fixation pin configured on a side of the attachment base plate opposite from the receiving device, wherein the fixation pin is insertable into a fixation opening of the cover.
 25. The device according to claim 20, wherein the cover has a fixation device.
 26. The device according to claim 20, wherein the orifice is surrounded by a seal with a positive fit.
 27. A method for galvanic production of a protective layer featuring hard material particles on a component of a turbomachine, comprising the steps of: a) attaching an opening of a pouch-, bag- or sack-like receiving device filled with hard material particles over and around a region of the component, wherein the receiving device is made of a net-, screen- or non-woven-like material that is pervious to an electrochemical coating solution and has a mesh size smaller than a diameter of the hard material particles; b) placing a region of the component into an immersion bath with the electrochemical coating solution and applying a voltage for forming a metallic matrix layer on the region of the component with embedding of the hard material particles; and c) galvanically forming a filler layer between the embedded hard material particles; wherein the receiving device is connected in a region of the opening to an attachment base plate such that the opening of the receiving device corresponds with an opening in the attachment base plate; wherein the attachment base plate is removably fastened to a cover; and wherein the cover has an orifice within which the region of the component is received and the opening of the attachment base plate and the opening of the receiving device are positioned over the orifice.
 28. The method according to claim 27, wherein, in process step c), a rotation of the component is carried out around an axis of rotation, wherein the axis of rotation of runs horizontally.
 29. The method according to claim 27, wherein the cover is removably fastened to the component prior to process step a).
 30. The method according to claim 27, wherein the electrochemical coating solution used in process step b) contains nickel.
 31. The method according to claim 27, wherein the hard material particles are made of boron nitride, ceramic, titanium carbide, tungsten carbide, chromium carbide, aluminum oxide or zirconium oxide or a mixture thereof.
 32. The method according to claim 27, wherein the filler layer fills in spaces between the hard material particles and wherein the hard material particles are integrated with 65-90% of their volume into the filler layer.
 33. The method according to claim 27, further comprising the step of, prior to process step a), cleaning and/or covering of the region of the component and/or chemical pretreatment of the region of the component. 